In many applications, it is necessary to produce, from a mineral material, grains, the dimensions of which are contained within clearly determined limits. When the grains are relatively large (between one millimeter and several tens of millimeters), it is known to produce them by breaking and to classify them according to different grades by screening. When the starting material has to be comminuted to powder (between one micron and several tens of microns), crushing is carried out, generally after several stages of breaking and grinding, followed by grading, for example by means of one or more pneumatic separators.
To produce relatively large grains and powder simultaneously, at least two comminuting apparatus have to be used: a breaker and a grinder.
The object of the invention is to permit the simultaneous production of several fractions of different grain sizes, ranging from a fraction the grains of which are of a size of possibly up to several tens of millimeters to a fraction the grains of which are of a size in the order of one micron to several hundreds of microns, by means of a single fragmenting apparatus and of grading apparatus.